Principal Investigator

At a Glance

With the dust settled on the 117th Congress, an updated 2023 analysis from REPEAT Project looks back at the progress made by the historic legislative session and the gaps remaining on the U.S. pathway to net-zero greenhouse gas emissions. Led by Jesse Jenkins of the Princeton ZERO Lab, the project’s latest report concludes that the more than $500 billion in public spending and incentives unleashed by the Inflation Reduction Act and Bipartisan Infrastructure Law will double the pace of U.S. decarbonization and cut annual emissions to 37-41% below peak levels by 2030. This is historic progress, but still short of the 50% cut to which President Biden has committed the United States. The report also looks sector-by-sector at remaining emissions and ways the United States could close this remaining gap

Students and researchers in the ZERO Lab, led by Prof. Jesse Jenkins, work collaboratively to assemble a lego model of a solar PV array during a group retreat. From left to right: Malini Nambiar (G4, SPIA), Dr. Fangwei Cheng (associate research scholar), Emilio Cano Renteria (senior CEE), and Edmund “Ned” Downie (G2, SPIA).


Research Highlight

The Biden Administration took office in January 2021 with a promise to pursue a “whole of government” approach to tackle climate change and cut emissions of greenhouse gases at least 50% below peak levels by 2030 and to net-zero by 2050.

With the conclusion of the 117th Congress, which sat from January 2021 to January 2023, the United States has now made historic progress towards those goals with passage of the Bipartisan Infrastructure Law, also known as the Infrastructure Investment and Jobs Act, and the Inflation Reduction Act (IRA). The two bills represent a sizable public investment to accelerate the clean energy transition, and total well over $500 billion over the next ten years. They provide incentives for nearly the entire suite of clean energy and climate mitigation solutions, including clean electricity and fuels, hydrogen, carbon capture, electric vehicles, building efficiency and electrification. This package of laws represents a turning point in U.S. decarbonization efforts—but how far do they get us on the path to net-zero?

Over the past two years, the REPEAT (Rapid Energy Policy Evaluation and Analysis Toolkit) Project, led by Jesse Jenkins, has consistently provided regular, timely and independent environmental and economic evaluation of federal energy and climate policies. Offering near real-time analysis of Congressional legislation as it was debated and enacted, the REPEAT Project established itself as a critical resource that has shaped policy negotiations, reporting and public understanding of federal policy making. Throughout the 117th Congress, the REPEAT Project released multiple analyses of proposed legislation, frequently publishing new analysis within days or weeks of major milestones in the progression of each piece of legislation through the Senate and House of Representatives. The Project’s reports have been accessed thousands of times and their analysis has been featured in dozens of news stories to date (, ranging from The New York Times and Washington Post to Nature, Axios and The New Yorker.

Now, with the dust settled on the 117th Congress, the REPEAT Project is releasing a new report that takes a revised and more careful look at the progress made to date, and the gaps that remain. REPEAT analysis concludes that the package of laws passed by the 117th Congress could roughly double the pace of decarbonization in the United States to about 4% per year, cutting U.S. greenhouse gas emissions to about 37-41% below peak historical levels reached circa 2005. That gets the U.S. much closer to the goal of a 50-52% reduction in emissions targeted by the Biden Administration in the United States’ National Determined Contribution to the UN Framework Convention on Climate Change. Yet gaps remain.

Figure 1.1.
Historical and modeled net U.S. greenhouse gas emissions, 2005-2035.2021).

The REPEAT Project highlights the potential for additional emissions reductions by accelerating the retirement of remaining coal-fired power plants and substituting natural gas-fired power generation (~0.2 GtCO2 -e/year in 2030). This step could improve industrial process efficiency (~0.1 GtCO2 -e/ year) and additional cost-effective abatement of methane pollution in the oil and gas sectors and make improvements in carbon uptake in agricultural and forestry lands (~0.2-0.3 GtCO2 -e/year). In total, these measures could get the U.S. within striking distance of 2030 climate goals and on track for net-zero emissions by 2050.

With support from the Hewlett Foundation, REPEAT plans annual updates in 2023 and 2024 on the United States’ progress on the path to net-zero. This will include analyses of proposed and finalized federal regulations and a stock take of the latest changes in costs and macro-economic conditions. Find the latest analysis and data at

Figure 1.2.
Difference in sectoral emissions vs. net-zero pathway (including land carbon sinks, non-CO2 abatement of greenhouse gases, buildings, industry, power and transportation).